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Date: Mon, 16 Jan 2012 21:31:25 +0100
From: Stephane Carrez <Stephane.Carrez@gmail.com>
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To: AdaMagica <christ-usch.grein@t-online.de>
Subject: Re: : Ada Utility Library 1.4.0 is available
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Date: 2012-01-16T21:31:26+01:00
List-Id: <comp.lang.ada>

Hi!

On 01/16/2012 09:10 AM, AdaMagica wrote:
> Hm, I looked at your beans, and I do not see the value of this.
> What's the advantage of returning components with string names versus
> returning them as usual?
> First of all, the components are visible. If they aren't, why not just
> use
>
> function Radius (B: Compute_Bean) return Float;
>

The purpose of these Ada beans is to be able to give access to
object values and object methods from withing a presentation layer.

The benefit of Ada beans comes when you need to get a value or invoke
a method on an object but you don't know at compile time the object or method.
That step being done later through some external configuration or presentation file.

In this case, you need somehow to dynamically retrieve the members of an object
(hence the Get_Value) and see what methods it exposes (hence the Get_Method_Bindings).

In a presentation page, the Ada bean values could be referenced as follows:

   Height: #{compute.height}
   Radius: #{compute.radius}

which triggers a call to Get_Value with the 'height' or 'radius' names on
an object registered under the name 'compute'.

To learn more on this presentation topic, I invite you to look at the following article:

http://blog.vacs.fr/index.php?post/2011/03/21/Ada-Server-Faces-Application-Example


Stephane